I've often heard it suggested that players wear down over the course of a season.

When I wrote about whether players elevate their game in the playoffs, multiple people in the comments argued that players can and should conserve energy during the regular season. It's a particularly common suggestion for older players, who are presumed to be more prone to fatigue. Guys like Jaromir Jagr and Teemu Selanne hate taking days off, but players and coaches are so convinced that they will wear out that they insist on it.

I'm not a physiology expert by any means, so I'm not qualified to make direct assessments of whether older players will suffer more cumulative fatigue than younger players would. However, I am capable of looking at whether such fatigue is born out in the stats.

Maintaining production

The first thing to decide is what effect of fatigue we're looking for. I see two distinct questions:

Does an older player who plays every game wear down and produce less later in the season?

Does fatigue lead to major injuries that cause players to miss large chunks of time?

To address the first question, I pulled a list of forwards since the last lockout who a) were 36 or older, b) missed no more than five games, and c) played at least 15 minutes a game. That last criterion is both because the heavy-minutes guys are most likely to show a fatigue effect if one exists and because my simple look at points will be a more viable way to assess fatigue in top-6 guys than grinders.

That left me with 44 top-6 elders to analyze. Collectively, they had 2425 points in 3543 games, or an average of 0.68 points per game. So what we're looking for is whether they were above 0.68 points per game early in the season and below that number later in the season. Here's a look at their production by 10-game segment of the player's season:

Segment

Games

Points

PPG

Games 1-10

440

304

0.69

Games 11-20

440

288

0.65

Games 21-30

440

313

0.71

Games 31-40

440

329

0.75

Games 41-50

440

283

0.64

Games 51-60

440

299

0.68

Games 61-70

440

282

0.64

Games 71-82

463

327

0.71

Or in graphical form:

I find it hard to look at that data and argue that older players playing nearly every game wear down and produce less down the stretch.

Staying healthy

The second question -- does rest help players avoid injury -- is tougher to answer. Obviously the answer is yes in some trivial sense; players get hit in every game, so skipping a game means skipping a chance to get hurt. But the discussion here is about a deeper question of fatigue and overuse; we want to see whether these old, worn out players suffer more injuries later in the season.

This gets challenging to dig into because there are a lot of reasons a player might might miss a game. Let's start by again narrowing things down to the high-scoring players (>0.5 PPG) who teams want in the lineup, who aren't likely to be scratched unless injury forces them out of the lineup.

Those 89 players collectively had 73 spans where they missed more than a week of play, which we'll presume were because of injury in most cases. The breakdown of when those spans began is as follows:

Month

Injuries

October

13

November

16

December

19

January

10

February

11

March

4

Admittedly, this is a crude pass at things. Disruption from effects like a tendency of players to fight through injury late in the season prevents me from making definitive statements about a cumulative effect of injury. But remember that whatever injuries they might be playing through didn't seem to result in decreased production.

I suppose it could be argued that by narrowing things down to the players who play the whole season or score a half-point per game, I've already limited the focus to players who are unusually able to survive the grind. And that may be true, but a) I'm not sure people really worry about whether Jamal Mayers wears down at the end of the year, and b) I'd like to see some evidence on the other side beyond "I'm 37 years old and after one hard skate I'm all sore; a whole NHL season is brutal just to think about."

I don't doubt that players feel worse by the end of the year as a result of accumulated bruises and strains, and this might be particularly true of older players whose bruises and strains don't heal as fast. However, if they're playing just as many games and scoring just as much as they did at the start of the year, are we sure that the grind of a long season affects their contributions on the ice?

A useful effort, Eric, but I think this method is pretty plainly rejecting precisely the players people are talking about.

For example, a coach who is concerned about an older player's ability to function late in the season will start by trying to sit him during difficult stretches earlier in the year. Double-headers, excessive road trips, etc. They may often do that and say they're giving them some time to repair injury X or somesuch. This could show up as rest at different points in the season, depending on how their bodies were bearing up, and how the team was doing, etc.

Then, in game, they may well ease back the throttle on their ice-time, if a game looks to be out-of-reach one way or another.

Also, I'm not sure why this is considered an unreasonable thing for a coach to do. Every coach sits goalies from games so they can rest. Same with shifts, they adjust game to game depending on whether a player "has it" that night. This is absolutely standard for what we know about athletes and sports performance, it varies over time within a year and across a career. By the time you're 36, you're simply not going to have quite the physical performance you had at 24. Thing is, you may have an even better mind for the game, experience, etc.... and so, the key thing is to ensure that the body doesn't break, and that the mind has room to operate to help make up any missing edge, once you're into key games.

I agree that a coach who is concerned about an older player might rest him early in the year. I agree that the coach might reduce their ice time in a blowout. Just because it's common practice and accepted wisdom doesn't make it right -- though it might raise the standard of proof for my analysis.

Similarly (though I'm not sure why this is related to the topic at hand), I agree that coaches will adjust game to game on whether a player "has it" that night, though I would say that this is standard for what we believe about athletes and sports performance rather than what we know -- I think it's quite possible, and maybe even likely, that when we say someone "has it" that night, we are simply overinterpreting variance. But this is off-topic.

The only part of your comment that directly addresses what I've said is when you say my method rejects the players people are talking about -- a concern that I acknowledged in the piece. For sure that's a possibility, but I think it's a bit strong for you to state it as fact.

We see no drop-off at all in production over the course of a season for the guys who play 77+ games and 15 minutes per game at age 36. So for you to believe that it's not a general truth, you would have to believe that:

b) Coaches are efficient at identifying such talent and rarely ask players who lack that durability to play 77+ games (otherwise, the players they mistakenly overburdened would show a decline and we would find evidence for fatigue in the group I studied).

Both of those might be true, but I don't really see any evidence to support this perspective.

The group of 15 min/game players who were kept under 77 games is: Arnott, Bertuzzi, Draper, Fedorov, Holmstrom, Jagr, Koivu, Langenbrunner, LeClair, Nieuwendyk, Nolan, Roberts, Stillman, and Sundin. How many in that group fell short of 77 games because the coach was giving them extra days off, rather than because they were injured? What makes you so sure that those players would have faded down the stretch if they had been allowed to play 77+ games?

I admit that the data here isn't conclusive, and I said as much in the article. But I don't see how, in the face of data showing that players who were asked to play a whole season at an old age didn't see their production drop at all, you can be 100% positive that old players wear out over the course of a season.

Interesting wrinkle to this argument: should a goaltender play 82 games? Once again, any investigation would be problematic, since most goaltenders playing 70+ games are certainly qualified to do so and probably won't show "fading" problems. But I think it's a relevant question to pose here.

I think this is pretty compelling evidence that older players tend not to fatigue as the season goes on, though we do see a small decline if we divide the season into two halves (0.70 in the first half and 0.67 in the second). I'd be interested to know how these numbers compare to the median as well as the average.

I'd also be interested to see the average goals per game for each segment. I would guess that the number of goals per game decreases as the season progresses, which would make the staying power of these oldsters even more impressive.

Takes a set of high-workload goalies, notes that their performance in March and April is no worse than the rest of the year (arguably better). However, if you narrow things down to just the guys who played 75+ games in a year, the performance after game 70 is a bit weaker than the rest of the year.

Bryzgalov, Rinne, and Lundqvist all show a gradual drop in performance with increasing number of consecutive games played. Kiprusoff, the clear games-played leader, does not show that drop (though the data is a bit noisy).

Overall, it's not an entirely clear picture, but it seems like the story in the data is that fatigue won't be an issue if the goalie gets the occasional off day and ends up with ~65-70 games, but that when off days start to be weeks apart and the games played total goes into the mid-70's, performance might suffer.